The present invention relates to magnetic recording media having high resistance to wear.
Thin film type magnetic recording media are fabricated by coating a thin ferromagnetic film on a base such as plastic film by the techniques of vacuum deposition, sputtering, ion plating and so on. Thin film type magnetic recording media or tapes are advantageous over the prior art coated type magnetic recording media in that the thickness of magnetic thin film may be reduced by a factor of one so that they are adapted especially for use in high density recording such as recording of video signal. However, ferromagnetic thin films are so hard that the wear and abrasion of a magnetic head results and the films themselves are also worn and abraided. In order to overcome this problem, a protective film must be formed on a ferromagnetic thin film. For instance, a monomolecular film of lubricant such as stearic acid is formed or a film of thermoplastic resins such as nylon including a lubricant is formed. These prior art protective films exhibit sufficient resistance to wear at relatively low temperatures and humidity as to 20.degree. C. and 50%, but the resistance to wear is considerably degraded at relatively high temperatures and humidity such as 30.degree.-50.degree. C. and at 80-90% so that the protective films are useless in practice. Environmental conditions under which home equipment such as home video tape recorders, audio recorders and so on are used are not specifically determined. That is, the equipment is often used at relatively high temperatures and at high humidity. It follows therefore that ferromagnetic thin films must be coated with a protective film which may effectively prevent rapid wear and abrasion of both a magnetic head and a magnetic recording medium.
When a ferromagnetic thin film is applied on a base, the latter is generally heated in vacuum so that various additives present at the vicinity of the surfaces of the base and evaporated and removed. As a result, the uncoated surface of the base lacks smoothness and exhibits increased insulation resistance so that triboelectric charging tends to occur very frequently. In addition, the magnetic thin film becomes electrically conductive so that the transport of magnetic recording medium is sometimes hindered by electrostatic interference. These are the main reasons why the uncoated surfaces of magnetic recording media must be treated.